Chief Constable Nick Gargan said that as an Independent Police Complaints Commission (IPCC) investigation was under way into allegations of misconduct in public office, he was unable to comment specifically on the police response.

"It is clear that there was a collective failure on the part of statutory agencies and others to protect Mr Ebrahimi and we cannot wait for all the various external investigative processes to run their course before we start learning lessons for the future," he said.

"We need to have some frank and candid local discussions with our partners and our communities about what we collectively can do to stop this happening again.

"Senior people in our own organisation have already put in place urgent actions to improve the way we respond to the vulnerable, handle reports of anti-social behaviour and identify repeat callers and victims and we will continue to talk to partners to improve the way we work together to protect the public."

The IPCC said six police officers and six civilian communications staff had been interviewed by investigators.

Three Pcs have been interviewed under caution on suspicion of misconduct in public office, while an inspector, sergeant and a constable - who dealt with Mr Ebrahimi while in custody - have been interviewed for gross misconduct.

The investigation against the inspector has since ceased.

A control room supervisor, a dispatcher and four call handlers who dealt with phone calls from Mr Ebrahimi have also been interviewed for gross misconduct.

IPCC commissioner Jan Williams said: "We have had ongoing dialogue with the Crown Prosecution Service and at the conclusion of our investigation I will be considering whether to send them a file of evidence in respect of any officers."

Mr Ebrahimi's sister, Manizhah Moores said her brother had suffered racial abuse while living in Bristol and his previous home had been the subject of an arson attack.

"On visiting Bijan's flat (in Capgrave Crescent), my sister witnessed him being called a 'foreigner', 'cockroach', 'Paki' and being told to 'go back to your own country' on many occasions by some of the people in the area," Mrs Moores said.

"We hope that nobody else ever has to witness an innocent disabled man being abused, taunted and tortured in the way that Bijan suffered.

"The question that now must be answered is whether Bijan's death could have been avoided had he been afforded the protection from the authorities he deserved.

"Lessons must be learned before other vulnerable lives are lost."

James, of Capgrave Crescent, Brislington, Bristol, pleaded guilty to murder and was jailed for life with a minimum term of 18 years' imprisonment.

Mr Justice Simon told him: "The circumstances of the murder of Bijan Ebrahimi and the subsequent burning of his body are deeply shocking.

"I am satisfied this was a vigilante crime.

"You decided wrongly that Mr Ebrahimi was a paedophile which put him outside the law.

"You thought you would take the law into your own hands.

"What you did had nothing to do with the law or justice.

"The law protects life.

"Yours was an act of murderous injustice."

Stephen Norley, 25, who lived next door to James, had pleaded guilty to assisting an offender after obtaining white spirit and helping drag Mr Ebrahimi's body to where it was set alight.

He was jailed for four years.

The court heard that James believed Mr Ebrahimi, an Iranian national who lived alone with his cat, was a paedophile.

The father-of-four, who lived two doors away, had threatened to take the law into his own hands unless police "dealt with the situation".

Prosecutor Andrew Langdon QC told the court: "Mr Ebrahimi used to take pictures and video films of his neighbours from his own property in a way which upset or offended them.

"It is clear he felt under siege and explained himself to the police as filming to gather evidence of the behaviour of his neighbours, which he found objectionable.

"Some of them alleged he was filming their children.

"This was derived by some to accusations of paedophilia.

"There is in fact no evidence whatsoever to support this claim."

Witnesses told police of a verbal confrontation between James and Mr Ebrahimi on the evening of July 11, with James telling his neighbour to stop taking pictures.

James was seen to enter Mr Ebrahimi's flat to confront him and was also overheard threatening to set fire to his home.

James flagged down PCSO Raymond Kelly, who was passing in a patrol car, and told him that his neighbour was "looking at my kids" and had taken a photograph of him.

"He said he was concerned about his children and wanted police action," Mr Langdon said.

"The officer explained it wasn't an offence to take adult photography.

"Mr James said if the police didn't deal with the situation he would deal with it himself.

"He repeated he wanted the situation sorted, he wasn't scared of being arrested of going to prison and would do anything to protect his children."

Mr Ebrahimi had also called police and Pcs Leanne Winter and Helen Paris arrived at the scene, just as James returned.

"He was furious and crying in anger," Mr Langdon said of James.

"He said: 'I will do time, I ain't having him takings pictures of my kids. She can look after the kids. If they ask why I am inside I will tell them I did it for them and they will be proud of me'."

As the officers arrested Mr Ebrahimi for "his own safety", he told them: "I can't believe you are arresting me when I haven't done anything."

Mr Langdon said: "As he was led away, the neighbours began cheering.

"Some were shouting abuse."

An eyewitness told Pc Winter: "Everyone seemed to be out of control.

"It was like they were a posse or a vigilante group or a witch hunt."

Mr Ebrahimi was released without charge and returned home the following day.

"During the course of the evening of July 12, Mr Ebrahimi made a number of calls to police reporting hostile behaviour," Mr Langdon said.

"For one reason or another, these messages were not responded to.

"At 1.57am he sent an email to the local beat manager saying he was being called 'nasty things' and did not feel safe at home.

"Regrettably that was not a message that was read until after his death."

Later that day, Mr Ebrahimi's neighbours held a party outside the block of flats, with alcohol being consumed.

That evening, James stood outside Mr Ebrahimi's flat and exposed himself to him, shouting "you think you have police protection".

Mr Ebrahimi came to the door of his flat before retreating inside, as neighbours loudly described him as a "nonce".

James and Norley's partners were overheard saying Mr Ebrahimi "was a paedophile and didn't deserve to live".

At around 11pm, James locked his partner and children inside their flat and told them not to come out.

The court heard that it was unclear how the attack on Mr Ebrahimi started, but witnesses saw James repeatedly stamp on his head with his right foot, telling him "have some of that".

At 1.35am the following day, CCTV captured a blaze starting, which burnt for 10 minutes until it was distinguished by an attending paramedic.

By this time, James and Norley had taken off their blood-splattered clothes and thrown them down a nearby lane before returning home.

James told his partner: "We set him on fire.

"He is not going to take photos any more.

"Tell the girls I did it for them and you.

"We took care of things."

He later told police: "I punched him first, then he went to the ground then I punched him some more.

"Then I kicked him."

A post-mortem examination report found Mr Ebrahimi suffered "multiple heavy blows to the face and head" and had died before he was set alight.

Simon Morgan, defending James, said a family member close to the defendant had been subjected to sexual abuse, which may have fuelled his misconceptions about Mr Ebrahimi.

"He is devoted to his children and is extremely protective of them," he said.

"Clearly it was a huge loss of temper and the violence clearly erupted suddenly.

"The enormity of what he has done is clear and he entirely accepts his behaviour in reaction to this particular aspect."

Michael Fitton QC, defending Norley, said he was a hard-working father-of-two with glowing references from his employer, a fruit and veg wholesaler in Bristol.